There are a number of different timing systems and devices, generally referred to as time-temperature indicators (TTIs), which can be used to monitor the exposure of objects to a range of temperatures over a specified period of time. Time-temperature indicators can have a number of different applications for indicating when an event or activity needs to take place. For example, time-temperature indicators have applications for indicating when the perishable materials have expired and need to be thrown out. Time-temperature indicators also have applications for general inventory management, for monitoring projects, activities and a host of other time and/or temperature dependent events. Therefore, there is a continued need to develop reliable timing systems and devices which can be used for a variety of different applications.
Color changing labels exist which utilize an electro-chemical reaction to deplete a thin metallic film which upon depletion allows for a visual discernment of whatever resides beneath. Such labels are manufactured in a variety of configurations but may suffer from manufacturing, depletion, and depletion problems. Additionally, such device may be unduly susceptible to unwanted external variables.